The objectives of this study are to characterize the uteroplacental circulating effects of exogenously administered prostaglandins in conscious pregnant sheep. Timed gestation Dorset sheep are utilized at 120-125 days gestation; electromagnetic flow transducers are placed on the common intra-abdominal umbilical vein and the main uterine artery of the pregnant horn. Venous and arterial catheters are placed in fetal and maternal circulation and all leads are exteriorized. At 72 hours postoperatively, prostaglandin F2 alpha, prostaglandin E2 or prostaglandin A1 are administered to the fetus or mother.